Reduced uncorrectable memory errors

ABSTRACT

Uncorrectable memory errors may be reduced by determining a logical array address for a set of memory arrays and transforming the logical array address to at least two unique array addresses based, at least in part, on logical locations of at least two memory arrays within the set of memory arrays. The at least two memory arrays are then accessed using the at least two unique array addresses, respectively.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application is a continuation of U.S. application Ser. No.13/792,597 filed Mar. 11, 2013. Said application Ser. No. 13/792,597 ishereby incorporated by reference herein in its entirety.

BACKGROUND

The present subject matter relates to semiconductor memories, and morespecifically, to reducing uncorrectable memory errors in semiconductormemories by organizing error correction codewords.

Many types of semiconductor memory are known. Some memory is volatileand will lose its contents if power is removed. Some memory isnon-volatile and will hold the information stored in the memory evenafter power has been removed. One type of non-volatile memory is flashmemory which stores charge in a charge storage region of a memory cell.Some flash memory cells store a single bit of information per cell, butit is becoming more and more common for a flash memory cell to storemore than one bit of information by setting a threshold voltage of thecell to one of 2^(n) levels to store n bits of information.

Another type of memory is phase change memory (PCM). PCMs utilize aphase change material having a non-conductive amorphous state and aconductive crystalline state. A PCM cell may be put into one state orthe other to indicate a stored value. By providing a potential acrossthe PCM cell, the state of the PCM cell can be determined by measuringcurrent flowing through the PCM cell. A PCM cell has a much higheron-current than off-current.

Some memory technologies are organized into cross-point arrays, where anarray of memory cells are densely packed and are individually coupled toa unique pair of control lines. An individual memory cell is coupled toone row line that is oriented in one direction, such as a word line, andone column line that is oriented in a perpendicular direction, such as abit line. Some memories may be organized as an array of cross-pointarrays, where the individual cross-point arrays are very densely packedbut may include some circuitry between the individual cross pointarrays.

Some memory technologies may be sufficiently reliable that no errorcorrection is necessary for many applications. In other technologies,the reliability of an individual memory cell may be low enough that anapplication of the memory may include redundant memory cells and errorcorrection and/or detection information may be stored in the redundantmemory cells. One common form of memory error correction is Hammingcodes, where a set of parity bits is included that allow any single biterror in the codeword to be corrected. A Hamming code requires n+1parity bits to protect 2^(n) bits, so 6 bits may be used to protect a 32bit data word. Many other types of error correction codes are wellknown, including, but not limited to, Reed-Solomon codes andBose-Chaudhuri-Hocquenghem (BCH) codes. Depending on the size of thepage, or codeword, of data, the number of error correcting codes thatare included, and the type of codes chosen, one or more errors may becorrectable or simply detected within a codeword.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are incorporated in and constitute partof the specification, illustrate various embodiments. Together with thegeneral description, the drawings serve to explain various principles.In the drawings:

FIG. 1 shows block diagram of an embodiment to transform addresses toreduce uncorrectable errors in a memory;

FIG. 2 shows a diagram of an embodiment of distribution of bits of acodeword across an array of memory arrays;

FIG. 3 shows a diagram of an alternative embodiment of distribution ofbits of a codeword across an array of memory arrays;

FIG. 4 is a block diagram of an embodiment of an electronic systemorganized to reduce uncorrectable errors in a memory;

FIG. 5 is a flowchart of an embodiment of a method to reduceuncorrectable errors in a memory;

FIG. 6 is a flowchart of an alternate embodiment of a method to reduceuncorrectable errors in a memory; and

FIG. 7A and 7B are block diagrams of an embodiment of a memory organizedto reduce uncorrectable errors in a memory.

DETAILED DESCRIPTION

In the following detailed description, numerous specific details are setforth by way of examples in order to provide a thorough understanding ofthe relevant teachings. However, it should be apparent to those skilledin the art that the present teachings may be practiced without suchdetails. In other instances, well known methods, procedures andcomponents have been described at a relatively high-level, withoutdetail, in order to avoid unnecessarily obscuring aspects of the presentconcepts. A number of descriptive terms and phrases are used indescribing the various embodiments of this disclosure. These descriptiveterms and phrases are used to convey a generally agreed upon meaning tothose skilled in the art unless a different definition is given in thisspecification. Reference now is made in detail to the examplesillustrated in the accompanying drawings and discussed below.

FIG. 1 shows a block diagram of an embodiment to transform addresses toreduce uncorrectable errors in a memory. Circuitry 100 may receive anaddress for a memory access. Depending on the embodiment, the addressmay include a word address 101 to identify a word of data within thememory system, and a bit address 102 that may identify a bit of datawithin the word of data. If the data is accessed in an organization thatis wider than a bit, the bit address 102 may identify a larger group ofdata, such as a byte, instead of an individual bit. A word of data, or acodeword, may include any number of data bits and any number of bitsdedicated to error correction and/or detection. The word of data may beof any size, depending on the embodiment, and may depend on a type oferror correction used. In some systems, a word of data may be spreadacross multiple memory devices. While any size of codeword may be used,in some embodiments a codeword of between about 1024 and about 4096 bitsof data may be used. In some embodiments, an entire codeword of data maybe simultaneously accessed, but in other embodiments, multiple memoryaccesses may be performed to access the entire codeword. In someembodiments, the codeword may include multiple bits of data within asingle array of data that may not be accessed simultaneously. In someembodiments an array may be organized to allow multiple bits within thememory array to be accessed simultaneously, such as a row at a time.

A single memory device may include an array of memory arrays, and thecodeword of data may be distributed across multiple memory arrays withinone memory device. The word address 101 may include a physical address103 that may address a set of memory arrays, and a logical array address104 that may address a logical location within the individual memoryarrays of the set of memory arrays. To illustrate a simplistic example,a memory device may have 4 memory arrays that each store 4 bits ofinformation. Two bit words may be defined that include one bit ofinformation from two different memory arrays. In that example, thephysical address 103 would be a single bit long, to identify which setof two memory arrays is being addressed, and the logical array address104 would be two bits to identify which location in the memory arrays isbeing accessed. The bit address 102, would be a single bit to identifywhich bit within the word is addressed, for a total of 4 bits to addressthe 16 bits of data that can be stored in the memory device.

The physical address 103 may be decoded by a decode circuit 110, thatmay determine which memory arrays to access based on the physicaladdress 103. The decode circuit 110 may have outputs to enable thevarious memory arrays, such as a first enable line 114 and a secondenable line 116. An individual enable line 114, 116, may enable a singlememory array, or may enable more than one memory array, as shown.

In some embodiments, the mapping of the physical address 103 to sets ofmemory arrays may be fixed at design time, and may be based on aphysical arrangement of the memory arrays within a memory device. Inother embodiments, a control register 118, which may be programmed withconfiguration information, may be used to map the physical address 103to a set of memory arrays. The control register 118 may be programmedwith information based on error rates of the various memory arrays todistribute the memory arrays with higher error rates across multiplecodewords to reduce the number of uncorrectable errors. In someembodiments, the control register 118 may be programmed during amanufacturing test process, before or after packaging. In someembodiments, the control register 118 may be programmed after the memorydevice has been integrated into an electronic system, such as duringmanufacturing of the system, or even during operation of the system. Thecontrol register 118 may be built with any type of storage technology,but in many embodiments, the control register 118 may be non-volatile sothat the values programmed into the control register 118 can bemaintained even if power is not applied. In some embodiments, thecontrol register 118 may be one-time programmable, such as fuse links oranti-fuse links, but other embodiments, may use flash memory cells, PCMcells or any other type of non-volatile memory that may allow data to bewritten into the control register 118 more than once.

The logical array address 104 may be transformed into multiple differentarray addresses by transform circuitry. In the embodiment shown, a firsttransform circuit 121 uses a first logical location 122 within thecodeword, to generate a first array address that includes a first columnaddress 123 and a first row address 124. Depending on the embodiment,the first array address may be used to address one or more arrays thatmay contribute a bit of data to the codeword addressed. A secondtransform circuit 125 uses a second logical location 126 within thecodeword, to generate a second array address that includes a secondcolumn address 127 and a second row address 128.

Depending on the embodiment, the column address, such as the firstcolumn address 123, and the row address, such as the first row address124, may be a standard binary address bus allowing n address lines toidentify a single column or row out of 2^(n) possibilities, or may bepartially or fully decoded into more lines, such as one line per row orcolumn. Depending on the embodiment, the separate array addresses may beused to address one or more arrays that may contribute a bit of data tothe codeword addressed. So in some embodiments, the first column address123 and the first row address 124 may be coupled to multiple memoryarrays, including memory array 132, and the second column address 127and the second row address 128 may be coupled to multiple memory arrays,including memory array 134. The data from the memory arrays accessed maybe coupled to a multiplexor 140 that may select a single bit of data142, or multiple bits of data for a particular access.

The logical location of the array(s) coupled to a common array addressmay be based on a physical arrangement of the different memory arrayswithin a set of memory arrays that contain data used in a codeword, anarbitrary assignment of different values for the different memory arrayswithin the set, and/or may be based on values programmed into a controlregister, depending on the embodiment. As an example, an embodiment mayhave a word that is 1024 bits in size with the bits of the word storedas one bit per memory array in 1024 different memory arrays. The memoryarrays may be grouped as 64 groups of 16 memory arrays, with the 16memory arrays of a single group coupled to a common array address. Onetransform circuit may be provided per group, so there may be 64different transform circuits. The 64 different groups may be assigned alogical location ranging from 0 to 63 with the logical location for agroup provided to the transform circuitry that generates the arrayaddress for that group. The assignment may be done in any manner,although some embodiments may distribute the logical locations so thatthere is no duplication of logical locations.

The transform circuitry 121 may transform the logical array address 104to an array address based on the logical location, such as the firstlogical location 122. Any type of transformation may be used as long asthere are no two valid logical array addresses 104 mapped to the samearray address by a single transform circuit. One type of transformationthat may be used in some embodiments is the re-ordering of addresslines. In one embodiment, the array address may be obtained by acircular shift, or rotate, of the logical array address 104 by a numberof locations based on the logical location 122. As an example of atransformation using a circular shift, if there are n lines in thelogical array address, L, and the amount of shift performed by thetransform circuit is m, which may be based on the logical location ofthe array(s), the array address, A_(i), may be defined as:

A_(i)=L_((i+m) mod n)

In another embodiment, the upper lines of the logical array address 104may be rotated by a multiple of the logical location 122 to obtain thefirst column address 123, and the lower lines of the logical arrayaddress 104 may be rotated by a different multiple of the logicallocation 122 to obtain the first row address 124. In another embodiment,the lines of the logical array address 104 may be swapped in a differentpseudo-random arrangement in the different transform circuits. In someembodiments, some address lines may not be re-ordered. Any arrangementof address line re-ordering may be used, as long as there are at leasttwo different unique transforms performed to create at least two uniquemappings of the logical array address 104 to array addresses.

Another type of transformation that may be used in some embodimentsincludes performing an arithmetic operation on the logical arrayaddress. In one embodiment, the array address may be obtained by addinga multiple of the logical location to the logical array address anddiscarding any additional upper bits that are generated. As an exampleof such a transform, the array address A may be calculated from thelogical address L having n bits based on the logical location N where0≦N≦2^(n), and M is an odd number that is constant across the varioustransform circuits by the equation:

A=(L+N×M) modulo 2^(n)

Another example transformation may be represented by the equation:

A=(L×(2N+1)+3M modulo 2^(n)

Any other type of arithmetic operation may be performed as long as notwo logical array addresses are mapped to a single array address by thesame transform circuit.

Performing such a transform to the array addresses of the differentarrays that may contribute data to a codeword may reduce uncorrectableerrors. While some errors in a memory are located at random locationsdue to random manufacturing defects, some errors may be systemic.Systemic errors may be related to a memory cell's physical locationwithin a memory array. Causes of such systemic errors may be based on adistance of a cell from the edge of the memory array where the linedrivers and power connections are located, mask defects that may berepeated between memory arrays, or other systemic issues. Errorcorrection codes have a limited number of errors that can be detected orcorrected, depending on the embodiment. If a systemic error is based ona physical location of a cell within an array, a high percentage of thearrays may have a defective cell in that particular location. If notransformation of the address is performed, the same physical locationof respective memory arrays in the set of memory arrays may be mapped toa common codeword, which may lead to a number of errors in the codewordthat exceeds the number of bits that may be corrected, which may bereferred to as overloading the codeword with errors. By distributing thephysical locations of the bits of the codeword within the various memoryarrays, the impact of a systemic error may be reduced, which may reducethe number of uncorrectable errors in the memory.

In some embodiments where a codeword is distributed across multiplememory devices, the logical location may include an identifier of thememory device so that memory arrays in the same physical location ofdifferent devices may receive different array addresses. By doing this,systemic defects related to a physical location of a memory array withinan integrated circuit die may also be mitigated.

FIG. 2 shows a diagram of an embodiment of distribution of bits of acodeword across an array of memory arrays 200. The array of memoryarrays 200 may include any number of memory devices, such as the firstmemory device 210 and the second memory device 250. The memory devices210, 250 respectively include arrays of memory arrays that may begrouped in various ways. In the embodiment shown, the first memorydevice 210 includes multiple partitions such as the first partition 220,the second partition 230, and the third partition 240. The second memorydevice 250 also includes multiple partitions such as the first partition260, the second partition 270, and the third partition 280.

The various partitions may be distributed into groups of memory arraysso that a partition is a group of groups of memory arrays. The firstpartition 220 of the first memory device 210 includes a first group 221,a second group 222, and a third group 223. Likewise, the first partition260 of the second memory device 250 includes a first group 261, a secondgroup 262, and a third group 263. A group of memory arrays, such as thefirst group 221 of the first partition 220 of the first memory device210 may include one or more memory arrays, such as the first memoryarray 224, the second memory array 225 and the third memory array 226.Embodiments may include any number of partitions in a memory device,with a partition including any number of groups, and a group includingany number of memory arrays, or tiles, of memory. Other embodiments mayuse other organizations of the memory arrays having greater or fewerlevels of hierarchy in the organization.

In the embodiment shown, the small black squares indicate bits of datathat are assigned to a single codeword, such as data bit 227 in memoryarray 225 of the first group 221 of the first partition 220 of the firstmemory device 210, data bit 229 in memory array 228 of the second group222 of the first partition 220 of the first memory device 210, data bit235 in memory array 237 of the first group of the second partition 230of the first memory device 210, and data bit 267 in memory array 265 ofthe first group 261 of the first partition 260 of the second memorydevice 250. While all the memory arrays shown include a data bit of thecodeword, other memory arrays that may be in groups that are shown ornot shown, in partitions that are shown or not shown, in memory devicesthat are shown or not shown may be included in the array of memoryarrays 200 and may or may not include any data of the codewordillustrated.

For a single access, a physical address may identify two or more arrays,such as the memory arrays that include a black square. A logical arrayaddress may identify a logical location in the two or more arraysidentified by the physical address. In the embodiment shown, the logicalarray address is transformed based on the logical group number within apartition, without regard for which partition or which chip the group ofmemory arrays is in. As can be seen from the location of the blacksquare within the memory arrays, the array address for the variousmemory arrays within a group is the same. So the location of the blacksquares in memory array 224 and memory array 226 is the same as thelocation of the black square 227 in the memory array 225, because thosethree memory arrays are in the first group 221 of the first partition220 of the first memory device 220.

The location of the black square, which represents a data bit of thecodeword, for other memory arrays in the first group of any partition inany memory device of the embodiment shown is in the same location. Sothe physical location of the data bit 235 of memory array 237 of thefirst group of the second partition 230 of the first memory device 210,and the physical location of the data bit 267 of the memory array 265 ofthe first group 261 of the first partition 260 of the second memorydevice 260 is the same as the physical location of the data bit 227 ofmemory array 225 of the first group 221 of the first partition 220 ofthe first memory device 210. But the location of the data bit 229 of thememory array 228 in the second group 222 of the first partition 220 ofthe first memory device is different.

FIG. 3 shows a diagram of an alternative embodiment of distribution ofbits of a codeword across an array of memory arrays 300. The array ofmemory arrays 300 may include any number of memory devices, such as thefirst memory device 310 coupled to a chip identifier ID0 315, and thesecond memory device 350 coupled to a different chip identifier ID1 355.The memory devices 310, 320 include an array of memory arrays that maybe grouped similarly to the memory devices of FIG. 2. In the embodimentshown, the first memory device 310 includes multiple partitions such asthe first partition 320, the second partition 330, and the thirdpartition 340. The second memory device 350 also includes multiplepartitions such as the first partition 360, the second partition 370,and the third partition 380. The various partitions may be distributedinto groups of memory arrays so that a partition is a group of groups ofmemory arrays. The first partition 320 of the first memory device 310includes a first group 321, a second group 322, and a third group 323.Likewise, the first partition 360 of the second memory device 350includes a first group 361, a second group 362, and a third group 363.

In the embodiment shown, the logical array address is transformed basedon the logical group number within a partition, the partition numberwith a device, and the chip identifier of the device. As can be seenfrom the location of the black square within the memory arrays, thearray address for the various memory arrays within a group is the same,but that location is different for each group shown. So the physicallocation of the data word within a codeword, as represented by the blacksquares in memory array 324 and memory array 326 is the same as thelocation of the black square 327 in the memory array 325, because thosethree memory arrays are in the first group 321 of the first partition320 of the first memory device 320.

But the location of data word 329 in the memory array 328 of the firstpartition 320 of the first memory device 310 is different than thelocation of the data word 327 in the memory array 325 even though theyare in the same partition 320 of the same memory device 310. Similarly,the location of data word 335 in the memory array 337 of the secondpartition 330 of the first memory device 310 is different than thelocation of the data word 327 in the memory array 325 even though theyare in the same group number of the same memory device 310, and thelocation of data word 367 in the memory array 365 of the first partition360 of the second memory device 350 is different than the location ofthe data word 327 in the memory array 325 even though they are in thesame group number of the same partition number because they are indifferent memory devices.

FIG. 4 is a block diagram of an embodiment of an electronic system 400organized to reduce uncorrectable errors in a memory. Supervisorycircuitry 401 is coupled to the memory device 410 with control/addresslines 403 and data lines 404. In some embodiments, data and control mayutilize the same lines. The supervisory circuitry 401 may include aprocessor, microprocessor, microcontroller, finite state machine, orsome other type of controlling circuitry. The supervisory circuitry 401may execute instructions of a program in some embodiments. In someembodiments, the supervisory circuitry 401 may be integrated in the samepackage or even on the same die as the memory device 410. In someembodiments, the supervisory circuitry 401 may be integrated with thecontrol circuitry 411, allowing some of the same circuitry to be usedfor both functions. The supervisory circuitry 401 may have externalmemory, such as random access memory (RAM) and read only memory (ROM),used for program storage and intermediate data or it may have internalRAM or ROM. In some embodiments, the supervisory circuitry 401 may usethe memory device 410 for program or data storage. A program running onthe supervisory circuitry 401 may implement many different functionsincluding, but not limited to, an operating system, a file system,memory block remapping, and error correction.

In some embodiments an external connection 402 is provided. The externalconnection 402 is coupled to input/output (I/O) circuitry 405 which maythen be coupled to the supervisory circuitry 401 and allows thesupervisory circuitry 401 to communicate to external devices. In someembodiments, the I/O circuitry 405 may be integrated with thesupervisory circuitry 401 so that the external connection 402 isdirectly coupled to the supervisory circuitry 401. If the electronicsystem 400 is a storage system, the external connection 402 may be usedto provide an external device with non-volatile storage. The electronicsystem 400 may be a solid-state drive (SSD), a USB thumb drive, a securedigital card (SD Card), or any other type of storage system. Theexternal connection 402 may be used to connect to a computer or otherintelligent device such as a cell phone or digital camera using astandard or proprietary communication protocol. Examples of computercommunication protocols that the external connection 402 may becompatible with include, but are not limited to, any version of thefollowing protocols: Universal Serial Bus (USB), Serial AdvancedTechnology Attachment (SATA), Small Computer System Interconnect (SCSI),Fibre Channel, Parallel Advanced Technology Attachment (PATA),Integrated Drive Electronics (IDE), Ethernet, IEEE-1394, Secure DigitalCard interface (SD Card), Compact Flash interface, Memory Stickinterface, Peripheral Component Interconnect (PCI) or PCI Express(PCI-e).

If the electronic system 400 is a computing system, such as a mobiletelephone, a tablet, a notebook computer, a set-top box, or some othertype of computing system, the external connection 402 may be a networkconnection such as, but not limited to, any version of the followingprotocols: Institute of Electrical and Electronic Engineers (IEEE)802.3, IEEE 802.11, Data Over Cable Service Interface Specification(DOCSIS), digital television standards such as Digital VideoBroadcasting (DVB)—Terrestrial, DVB-Cable, and Advanced TelevisionCommittee Standard (ATSC), and mobile telephone communication protocolssuch as Global System for Mobile Communication (GSM), protocols based oncode division multiple access (CDMA) such as CDMA2000, and Long TermEvolution (LTE).

The memory device 410 may include an array 416 of memory arrays 417,418. Address lines and control lines 403 may be received and decoded bycontrol circuitry 411. I/O circuitry 412 may couple to the data lines404 allowing data to be received from and sent to the supervisorycircuitry 401. Data read from the memory array 416 may be temporarilystored in read buffers 419. Address transform circuitry 413 may generatea first array address 414 that may be coupled to one or more memoryarrays 417 and a second array address 415 that may be coupled to one ormore memory arrays 418. The address transform circuitry 413 maytransform a logical array address that may be received from thesupervisory circuitry on at least a portion of the address lines 403 tothe at least two array unique array addresses 414, 415 based, at leastin part, on logical locations of the memory arrays 417, 418 within theset of memory arrays.

Data stored in the array of memory arrays 416 may be arranged intocodewords that include error correction codes. Once a codeword has beenread from the array of memory arrays 416, one or more errors may becorrected in the data of the codeword. In some embodiments, the errorcorrection may be performed within the memory device 410. In otherembodiments, the supervisory circuitry 401 may read the data of acodeword from the memory device 410 using one or more memory accesscommands, and then the supervisory circuitry 401 may correct one or moreerrors in the data of the codeword.

The system illustrated in FIG. 4 has been simplified to facilitate abasic understanding of the features of the memory. Many differentembodiments are possible including using a solid state drive controlleras the supervisory circuitry 401 and I/O circuitry 405 to control aplurality of memory devices 410 to act as a solid state drive. Anotherembodiment may use a processor for the supervisory circuitry 401 and I/Ocircuitry 405 with additional functions, such as a video graphicscontroller driving a display, and other devices for human oriented I/Omay be utilized to implement a personal computer, personal computer orsmart phone.

FIG. 5 is a flowchart 500 of an embodiment of a method to reduceuncorrectable errors in a memory. The method starts at block 501 anddetermines a logical array address at block 502. The logical arrayaddress in some embodiments may be a portion of an address that is sentfrom a processor or supervisory circuitry that may be coupled to amemory device. The logical array address may be transformed at block 503into at least two unique array addresses based, at least in part, onlogical locations of at least two memory arrays within the set of memoryarrays. The transforming may be performed by re-ordering address linesin some embodiments. In other embodiments, the transforming may beperformed by one or more arithmetic operations using the logical arrayaddress. In some embodiments, the transforming may also be based onvalues programmed into a control register.

The unique array addresses may include row addresses and columnaddresses. An array address is unique if its combined row address andcolumn address is different from other array addresses. So two arrayaddresses are unique if the first row address is different than thesecond row address, or the first column address is different than thesecond column address.

The array addresses may be used to access memory arrays at block 504.One array address may be coupled to a group of memory arrays of the setof memory arrays. A location of the group of memory arrays within theset of memory arrays may be used as a logical location for thetransforming of the logical array address. In some embodiments, a chipidentifier, which may differentiate between multiple chips of a system,may be used as a part of the logical location. Data from the two or morememory arrays may be read to determine a word of data that includeserror correction codes and at least one error in the word of data may becorrected at block 505 before the flowchart 500 completes at block 506.

FIG. 6 is a flowchart 600 of an alternate embodiment of a method toreduce uncorrectable errors in a memory. The flowchart 600 begins atblock 601 and continues at block 602 by determining error rates of twoor more memory arrays in a memory device. In some embodiments, thedetermining of error rates of the two or more memory arrays may be doneas a part of a manufacturing test process on a stand-alone memory devicebefore it is integrated into a system. The manufacturing test may beperformed on the memory die before packaging or after it is integratedinto a package. In some embodiments, multiple memory die may beintegrated into a single package with a chip identifier inputidentifying a logical position of the die in the package. In otherembodiments, the determining of the error rates of the two or morememory arrays may be performed in a system environment after the memorydevice is integrated into a system such as into a computer, a tablet, asmart phone, or some other type of electronic system. The memory arraysmay be tested to determine their error rates in a system testenvironment, or during normal operation, and the testing may occur atthe time that the system is manufactured, or even after the system isdeployed. In some embodiments, the error rates may be based on datacollected during normal operation of the system, and made available tohelp determine how to map the two or more memory arrays into two or morecodewords.

Once the error rates of the two or more memory arrays have beenobtained, a mapping of the two or more memory arrays into two or morecodewords may be determined 603 based on the error rates. Memory arrayshaving higher error rates than other memory arrays may be distributedamong different codewords to distribute the errors so that they are morelikely to be correctable. Likewise, memory arrays having lower errorrates than other memory arrays may be distributed. By distributing thelikely errors among codewords, the number of errors that are likely tooccur in a single codeword may be reduced, which may reduce the numberof uncorrectable errors.

Once a desired mapping has been determined, a control register may beprogrammed 604 to map the two or more memory arrays into the two or morecodewords. The control register may use any type of storage technology,but may utilize non-volatile one-time programmable elements in at leastone embodiment. The programming may be performed at any time, such as apart of a manufacturing test process or in a system environment,depending on the embodiment. In operation, the memory device may respondto one or more memory accesses to allow a codeword of data to beretrieved from the memory device. Then at least one error may becorrected in the codeword of data. The flowchart completes at block 605.

FIG. 7A and 7B are block diagrams of an embodiment of a memory 700organized to reduce uncorrectable errors in a memory. The memory 700 maybe suitable for use with the method shown in FIG. 6. The memory 700includes control registers 701 and address transform circuitry 702 thatreceives an address 703 and uses data programmed into the controlregisters 701 to selectively enable the memory arrays 711, 712, 721,722. The memory arrays may be grouped into groups of memory arrays wheredata from a group of memory arrays is used in a codeword for errorcorrection. As described in flowchart 600, the memory arrays may betested to determine their error rates. Once the error rates aredetermined, the control register may be programmed to distribute thememory arrays with higher error rates among different codewords.

In FIG. 7A, the memory arrays may be tested and it may be determinedthat memory array 711 has the lowest error rate, memory array 722 hasthe second lowest error rate, memory array 721 has the second highesterror rate, and memory array 712 has the highest error rate. Once theerror rates have been determined, it may be determined that groupingmemory array 711 and memory array 712 into a first group 731, and memoryarray 721 and memory array 722 into a second group 732 may provide forreduced uncorrectable memory errors. Control register 701 may then beprogrammed with information to control the address transform circuitry702 to perform that mapping. So a first memory array 712 having a highererror rate than other memory arrays of the two or more memory arrays maybe mapped to a particular codeword and a second memory array 711 havinga lower error rate than other memory arrays of the two or more memoryarrays may be mapped to the same particular codeword.

In FIG. 7B, the memory arrays may be tested and it may be determinedthat memory array 712 has the lowest error rate, memory array 711 hasthe second lowest error rate, memory array 721 has the second highesterror rate, and memory array 722 has the highest error rate. Once theerror rates have been determined, it may be determined that groupingmemory array 711 and memory array 721 into a first group 741, and memoryarray 712 and memory array 722 into a second group 742 may provide forreduced uncorrectable memory errors. Control register 701 may then beprogrammed with information to control the address transform circuitry702 to perform that mapping.

The flowchart and/or block diagrams in the figures help to illustratethe operation of possible implementations of methods of variousembodiments. It should be noted that, in some alternativeimplementations, the functions noted in the block may occur out of theorder noted in the figures. For example, two blocks shown in successionmay, in fact, be executed substantially concurrently, or the blocks maysometimes be executed in the reverse order, depending upon thefunctionality involved.

Examples of various embodiments are described in the followingparagraphs:

An example method to reduce uncorrectable memory errors may includedetermining a logical array address for a set of memory arrays,transforming the logical array address to at least two unique arrayaddresses based, at least in part, on logical locations of at least twomemory arrays within the set of memory arrays, and accessing the atleast two memory arrays using the at least two unique array addresses,respectively. The transforming reduces uncorrectable errors in errorcorrection codewords that include data from the set of memory arrays. Insome example methods an error correction codeword includes at least abit of data, respectively, from memory arrays of the set of memoryarrays, and a common physical location in the at least two memory arraysis mapped to at least two different error correction codewords to reduceuncorrectable memory errors due to systemic errors in the set of memoryarrays overloading the error correction codeword with errors. Someexample methods may also include retrieving data of an error correctioncodeword from the set of memory arrays using the at least two uniquearray addresses, and providing the data of the error correction codewordfrom the set of memory arrays to a controller, wherein the controllercorrects one or more errors in the error correction codeword. In someexample methods the transforming includes re-ordering address lines ofthe logical array address. In some example methods the transformingincludes performing an arithmetic operation on the logical arrayaddress. In some example methods the transforming is also based, inpart, on values programmed into a control register. In some examplemethods a first unique array address includes a first row address and afirst column address, and a second unique array address includes asecond row address and a second column address, wherein the first rowaddress is different than the second row address, or the first columnaddress is different than the second column address. Some examplemethods may also include accessing a group of memory arrays within theset of memory arrays using a first unique array address of the at leasttwo unique array addresses. In some example methods the logicallocations of the at least two memory arrays include identifiers ofgroups of memory arrays within the set of memory arrays. In some examplemethods the logical locations of the at least two memory arrays furtherinclude chip identifiers. Any combination of the examples of thisparagraph may be used in embodiments.

An example integrated circuit includes means for determining a logicalarray address for a set of memory arrays, means for transforming thelogical array address to at least two unique array addresses based, atleast in part, on logical locations of at least two memory arrays withinthe set of memory arrays, and means accessing the at least two memoryarrays using the at least two unique array addresses, respectively,wherein the transforming of the logical array address reducesuncorrectable errors in error correction codewords including data fromthe set of memory arrays. In some example integrated circuits an errorcorrection codeword includes at least a bit of data, respectively, frommemory arrays of the set of memory arrays, and a common physicallocation in the at least two memory arrays is mapped to at least twodifferent error correction codewords to reduce uncorrectable memoryerrors due to systemic errors in the set of memory arrays overloadingthe error correction codeword with errors. Some example integratedcircuits also include means for retrieving data of an error correctioncodeword from the set of memory arrays using the at least two uniquearray addresses, and means for providing the data of the errorcorrection codeword from the set of memory arrays to a controller,wherein the controller is configured to correct one or more errors inthe error correction codeword. In some example integrated circuits saidmeans for transforming includes means for re-ordering address lines ofthe logical array address. In some example integrated circuits saidmeans for transforming includes means for performing an arithmeticoperation on the logical array address. In some example integratedcircuits a first unique array address includes a first row address and afirst column address, and a second unique array address includes asecond row address and a second column address, wherein the first rowaddress is different than the second row address, or the first columnaddress is different than the second column address. Some exampleintegrated circuits also include means for accessing a group of memoryarrays within the set of memory arrays using a first unique arrayaddress of the at least two unique array addresses. In some exampleintegrated circuits the logical locations of the at least two memoryarrays include identifiers of groups of memory arrays within the set ofmemory arrays. Any combination of the examples of this paragraph may beused in embodiments.

An example integrated circuit includes a set of memory arrays includingat least a first memory array and a second memory array, a first circuitto transform a logical array address into a first unique array addresscoupled to the first memory array based, at least in part, on a logicallocation of the first memory array within the set of memory arrays, anda second circuit to transform the logical array address into a secondunique array address coupled to the second memory array based, at leastin part, on a logical location of the second memory array within the setof memory arrays. In the example integrated circuit, data from the firstmemory array at the first unique array address and data from the secondmemory array at the second unique array address are included in aparticular error correction codeword to reduce uncorrectable errors inthe particular error correction codeword. In some example integratedcircuits a first error correction codeword includes data identified by afirst logical array address, and a second error correction codewordincludes data identified by a second logical array address, the firstcircuit transforms a first logical address to identify a particulararray location in the first memory array and the second circuittransforms a second logical address to identify the particular arraylocation in the second memory array, and a systemic error in theparticular array location in both the first memory array and the secondmemory array distributes errors between the first error correctioncodeword and the second error correction codeword to avoid overloadingeither the first error correction codeword or the second errorcorrection codeword with errors. Some example integrated circuits mayalso include a data interface to provide data of the particular errorcorrection codeword to a controller, wherein the controller isconfigured to correct one or more errors in the particular errorcorrection codeword. In some example integrated circuits the firstcircuit includes circuitry to re-order address lines of the logicalarray address. In some example integrated circuits the first circuitincludes circuitry to perform an arithmetic operation using the logicalarray address and at least a portion of the logical location of thefirst memory array within the set of memory arrays. In some exampleintegrated circuits the second circuit includes circuitry to perform thearithmetic operation using the logical array address and at least aportion of the logical location of the second memory array within theset of memory arrays. In some example integrated circuits the firstcircuit includes circuitry to transform the logical array address based,in part, on values programmed into a control register. In some exampleintegrated circuits the logical locations of the at least two memoryarrays include identifiers of groups of memory arrays within the set ofmemory arrays. Some example integrated circuits also include a chipidentifier input, wherein the logical locations of the at least twomemory arrays further include values received from the chip identifierinput. Any combination of the examples of this paragraph may be used inembodiments.

An example electronic system includes supervisory circuitry to generatememory read commands including a logical array address, and a memory,coupled to the supervisory circuitry, to respond to the memory controlcommands. The memory in the example electronic system may include a setof memory arrays, circuitry to transform the logical array address to atleast two unique array addresses based, at least in part, on logicallocations of at least two memory arrays within the set of memory arrays,the at least two unique array addresses coupled to the at least twomemory arrays, respectively, and circuitry to provide data identified bythe at least two unique array addresses from the at least two memoryarrays to the supervisory circuitry in response to the memory controlcommands. In the example electronic system the data identified by thelogical array address is included in a particular error correctioncodeword to reduce uncorrectable errors the particular error correctioncodeword, and the supervisory circuitry is configured to correct errorsin data of error correction codewords, including the particular errorcorrection codeword. In some example electronic systems at least twoerror correction codewords include data identified respectively by atleast two different logical array addresses, the circuit transforms theat least two different logical array addresses to respectively address acommon array location in the at least two memory arrays, and a systemicerror in the common array location in the at least two memory arraysdistributes errors among the least two error correction codewords toavoid overloading any one of the least two error correction codewordswith errors. In some example electronic systems the circuitry totransform the logical array address includes circuitry to re-orderaddress lines of the logical array address to create the at least twounique array addresses. In some example electronic systems the circuitryto transform the logical array address includes circuitry to perform anarithmetic operation using the logical array address and at least aportion of a logical location of a first memory array within the set ofmemory arrays to create a first unique array address to couple to thefirst memory array, and circuitry to perform an arithmetic operationusing the logical array address and at least a portion of a logicallocation of a second memory array within the set of memory arrays tocreate a second unique array address to couple to the second memoryarray. In some example electronic systems the circuitry includescircuitry to transform the logical array address based, in part, onvalues programmed into a control register. In some example electronicsystems the logical locations of the at least two memory arrays includeidentifiers of groups of memory arrays within the set of memory arrays.In some example electronic systems the memory is a first memory and theelectronic system may also include a first chip identifier coupled tothe first memory, a second memory coupled to the supervisory circuitry,and a second chip identifier coupled to the second memory. In someexample electronic systems the second memory includes a first memoryarray and a second memory array, a first circuit to transform thelogical array address into row and column addresses for the first memoryarray and the second memory array based, at least in part, on the secondchip identifier, and a second circuit to provide additional data fromthe first memory array and the second memory array to the supervisorycircuitry in response to the memory control commands. In some exampleelectronic systems the circuitry of the first memory transforms thelogical array address to the at least two unique array addresses based,at least in part, on the first chip identifier, and the supervisorycircuitry is configured to correct at least one error in a codewordincluding the data from the first memory and the additional data fromthe second memory. Some example electronic system may also include I/Ocircuitry, coupled to the supervisory circuitry, to communicate with anexternal device. At least one example electronic systems is a solidstate drive. Any combination of the examples of this paragraph may beused in embodiments.

An example method to reduce uncorrectable memory errors may includeobtaining error rates of two or more memory arrays in a memory device,determining a mapping of the two or more memory arrays into two or morecodewords based on said error rates, and programming a control registerto map the two or more memory arrays into the two or more codewords,wherein said mapping reduces uncorrectable errors in the two or morecodewords. In some example methods, values programmed into the controlregister configure the memory device to map a first memory array havinga higher error rate than other memory arrays of the two or more memoryarrays to a particular codeword, and map a second memory array having alower error rate than other memory arrays of the two or more memoryarrays to the particular codeword. In some example methods thedetermining and the programming are performed as a part of amanufacturing test process on the memory device. In some example methodsthe determining and the programming are performed in a systemenvironment. Some example methods may also include retrieving a codewordof data from the memory device, and correcting at least one error in thecodeword of data. Any combination of the examples of this paragraph maybe used in embodiments.

An example electronic system includes means for obtaining error rates oftwo or more memory arrays in a memory device, means for determining amapping of the two or more memory arrays into two or more codewordsbased on said error rates to reduce uncorrectable errors in the two ormore codewords, and means for programming a control register to map thetwo or more memory arrays into the two or more codewords. Some exampleelectronic systems may also include means for programming values intothe control register to configure the memory device to map a firstmemory array having a higher error rate than other memory arrays of thetwo or more memory arrays to a particular codeword, and map a secondmemory array having a lower error rate than other memory arrays of thetwo or more memory arrays to the particular codeword. Some exampleelectronic systems may also include means for retrieving a codeword ofdata from the memory device, and means for correcting at least one errorin the codeword of data. Any combination of the examples of thisparagraph may be used in embodiments.

As used in this specification and the appended claims, the singularforms “a”, “an”, and “the” include plural referents unless the contentclearly dictates otherwise. Furthermore, as used in this specificationand the appended claims, the term “or” is generally employed in itssense including “and/or” unless the content clearly dictates otherwise.As used herein, the term “coupled” includes direct and indirectconnections. Moreover, where first and second devices are coupled,intervening devices including active devices may be located therebetween.

The description of the various embodiments provided above isillustrative in nature and is not intended to limit this disclosure, itsapplication, or uses. Thus, different variations beyond those describedherein are intended to be within the scope of embodiments. Suchvariations are not to be regarded as a departure from the intended scopeof this disclosure. As such, the breadth and scope of the presentdisclosure should not be limited by the above-described exemplaryembodiments, but should be defined only in accordance with the followingclaims and equivalents thereof

What is claimed is:
 1. A method to reduce uncorrectable memory errorscomprising: determining a logical array address for a set of memoryarrays; transforming the logical array address to at least two uniquearray addresses based, at least in part, on logical locations of atleast two memory arrays within the set of memory arrays; and accessingthe at least two memory arrays using the at least two unique arrayaddresses, respectively; wherein said transforming reduces uncorrectableerrors in error correction codewords comprising data from the set ofmemory arrays.
 2. The method of claim 1, wherein an error correctioncodeword comprises at least a bit of data, respectively, from memoryarrays of the set of memory arrays; and a common physical location inthe at least two memory arrays is mapped to at least two different errorcorrection codewords to reduce uncorrectable memory errors due tosystemic errors in the set of memory arrays overloading the errorcorrection codeword with errors.
 3. The method of claim 1, furthercomprising: retrieving data of an error correction codeword from the setof memory arrays using the at least two unique array addresses; andproviding the data of the error correction codeword from the set ofmemory arrays to a controller; wherein the controller corrects one ormore errors in the error correction codeword.
 4. The method of claim 1,wherein a first unique array address comprises a first row address and afirst column address; and a second unique array address comprises asecond row address and a second column address; wherein the first rowaddress is different than the second row address, or the first columnaddress is different than the second column address.
 5. The method ofclaim 1, further comprising accessing a group of memory arrays withinthe set of memory arrays using a first unique array address of the atleast two unique array addresses.
 6. The method of claim 1, wherein thelogical locations of the at least two memory arrays comprise identifiersof groups of memory arrays within the set of memory arrays.
 7. Themethod of claim 6, wherein the logical locations of the at least twomemory arrays further comprise chip identifiers.
 8. An integratedcircuit comprising: a set of memory arrays comprising at least a firstmemory array and a second memory array; a first circuit to transform alogical array address into a first unique array address coupled to thefirst memory array based, at least in part, on a logical location of thefirst memory array within the set of memory arrays; and a second circuitto transform the logical array address into a second unique arrayaddress coupled to the second memory array based, at least in part, on alogical location of the second memory array within the set of memoryarrays; wherein data from the first memory array at the first uniquearray address and data from the second memory array at the second uniquearray address are included in a particular error correction codeword toreduce uncorrectable errors in the particular error correction codeword.9. The integrated circuit of claim 8, wherein a first error correctioncodeword comprises data identified by a first logical array address, anda second error correction codeword comprises data identified by a secondlogical array address; the first circuit transforms a first logicaladdress to identify a particular array location in the first memoryarray and the second circuit transforms a second logical address toidentify the particular array location in the second memory array; and asystemic error in the particular array location in both the first memoryarray and the second memory array distributes errors between the firsterror correction codeword and the second error correction codeword toavoid overloading either the first error correction codeword or thesecond error correction codeword with errors.
 10. The integrated circuitof claim 8, further comprising: a data interface to provide data of theparticular error correction codeword to a controller; wherein thecontroller is configured to correct one or more errors in the particularerror correction codeword.
 11. The integrated circuit of claim 8,wherein the first circuit comprises circuitry to re-order address linesof the logical array address.
 12. The integrated circuit of claim 8,wherein the first circuit comprises circuitry to perform an arithmeticoperation using the logical array address and at least a portion of thelogical location of the first memory array within the set of memoryarrays.
 13. The integrated circuit of claim 12, wherein the secondcircuit comprises circuitry to perform the arithmetic operation usingthe logical array address and at least a portion of the logical locationof the second memory array within the set of memory arrays.
 14. Theintegrated circuit of claim 8, wherein the first circuit comprisescircuitry to transform the logical array address based, in part, onvalues programmed into a control register.
 15. The integrated circuit ofclaim 8, wherein the logical locations of the at least two memory arrayscomprise identifiers of groups of memory arrays within the set of memoryarrays.
 16. The integrated circuit of claim 8, further comprising a chipidentifier input; wherein the logical locations of the at least twomemory arrays further comprise values received from the chip identifierinput.
 17. An electronic system comprising supervisory circuitry togenerate memory read commands comprising a logical array address; and amemory, coupled to the supervisory circuitry, to respond to the memorycontrol commands, the memory comprising: a set of memory arrays;circuitry to transform the logical array address to at least two uniquearray addresses based, at least in part, on logical locations of atleast two memory arrays within the set of memory arrays, the at leasttwo unique array addresses coupled to the at least two memory arrays,respectively; and circuitry to provide data identified by the at leasttwo unique array addresses from the at least two memory arrays to thesupervisory circuitry in response to the memory control commands;wherein the data identified by the logical array address is included ina particular error correction codeword to reduce uncorrectable errorsthe particular error correction codeword; and the supervisory circuitryis configured to correct errors in data of error correction codewords,including the particular error correction codeword.
 18. The electronicsystem of claim 17, wherein the memory is a first memory, the electronicsystem further comprising: a first chip identifier coupled to the firstmemory; a second memory coupled to the supervisory circuitry; and asecond chip identifier coupled to the second memory; wherein the secondmemory comprises: a first memory array and a second memory array; afirst circuit to transform the logical array address into row and columnaddresses for the first memory array and the second memory array based,at least in part, on the second chip identifier; and a second circuit toprovide additional data from the first memory array and the secondmemory array to the supervisory circuitry in response to the memorycontrol commands; wherein the circuitry of the first memory transformsthe logical array address to the at least two unique array addressesbased, at least in part, on the first chip identifier; and thesupervisory circuitry is configured to correct at least one error in acodeword comprising the data from the first memory and the additionaldata from the second memory.
 19. The electronic system of claim 17,further comprising: I/O circuitry, coupled to the supervisory circuitry,to communicate with an external device.
 20. The electronic system ofclaim 17, wherein the electronic system is a solid state drive.